U.S. Pat. No. 3,313,409 discloses an apparatus for inspecting glass containers in which a starwheel conveys containers in sequence through a series of inspection stations. At one of the inspection stations, selected dimensional parameters of each container are inspected by contacting the container with rollers coupled to sensors, and rotating the container about its central axis so that the sensors provide output signals that vary as a function of variation of the container parameters. Specifically, container height, sealing surface warp and dip, and cocked orientation of the container finish are measured by rollers that engage the container sealing surface as the container rotates. The rollers are coupled to LVDT sensors that provide analog electrical signals indicative of deviations or variations in level (height) at the sealing surface. These signals are fed to appropriate electronics to energize a reject plunger for separating a container from the conveyor line if the measurement signals depart from desired standards and specifications.
Although the inspection system disclosed in the noted patent, assigned to the assignee hereof, has enjoyed substantial commercial success, improvements remain desirable. The rollers in contact with the container sealing surfaces are subject to mechanical wear. The rollers may cause contamination at the sealing surface. The size of the rollers limits the size of containers in connection with which they may be employed, and the size (resolution) of level variations that can be detected. The moving parts require maintenance and repair. It is a general object of the present invention to provide an apparatus and method for inspecting the sealing surfaces of containers for variations in level at the container sealing surface that address and overcome the aforementioned deficiencies in the art.
More specifically, it is an object of the present invention to provide an apparatus and method for measuring level variations in the sealing surfaces of containers that employ electro-optical techniques in which the gauging apparatus does not contact the measurement surface. Another object of the present invention is to provide a method and apparatus of the described character that attains the foregoing objectives, while being economical to implement and reliable over an extended operating lifetime. Yet another and more specific object of the present invention is to provide an electro-optical non-contact method and apparatus for measuring the height of containers at the sealing surfaces, for measuring warp and dip at the sealing surfaces, and for measuring cocked finish of the containers.